Method and System for Maintaining Multiple PDN Network Connection During Inter-Technology Handover in Idle Mode

ABSTRACT

The present invention provides a method and system for supporting an optimized an idle mode handoff of user equipment from a 3GPP (EUTRAN) to a non-3GPP system (HRPD, cdma2000) where the user equipment washes to maintain connectivity with multiple PDN networks. Namely, during an idle mode registration of the user equipment with the non-3GPP system, the user equipment will provide an indication to the access node on the non-3GPP system so that the access point in that non-3GPP system contacts the appropriate entity (HSS or AAA) on the home network for the user equipment to download the addresses of the multiple PDN gateway addresses that are currently in use by the user equipment. This indication to the non-3GPP access node, the contact message from the access node to the home network, and the response from the home network to the access node on the non-3GPP system are novel features that are not shown in the prior art, and provide the access node with sufficient information to maintain multiple PDN connectivity to the user equipment during an idle mode handover.

RELATED APPLICATION DATA

This application is related to Provisional Patent Application Ser. No.61/039,252 filed on Mar. 25, 2008, and priority is claimed for thisearlier filing under 35 U.S.C. §119(e). The Provisional PatentApplication is also incorporated by reference into this utility patentapplication.

TECHNICAL FIELD OF THE INVENTION

A method and system for maintaining multiple PDN network connectionsduring inter-technology wireless handover in idle mode.

BACKGROUND OF THE INVENTION

When a mobile unit is traveling, it may need to be handed off from onenetwork to another. There are different types of wireless communicationsystems, such as general packet radio service (GPRS), global system formobile (GSM)/enhanced data rates for GSM evolution (EDGE) radio accessnetwork (GERAN), and long term evolution (LTE) evolved universalterrestrial radio access network (EUTRAN). LTE/EUTRAN system has adifferent physical layer and a different architecture from those systemspreceding it, i.e., GPRS, GERAN, or UTRAN. Since not all networks areidentical, a method for supporting the handoff between systems would bebeneficial.

United States Patent Publication Nos. US 2008/0268846A1 and2008/0192697A1 describe a prior art method and system for supporting ahandoff of user equipment from a GPRS/GERAN system to an LTE EUTRANsystem, and vice versa, respectively. These references include a FIG. 1exemplary diagram of a system including an LTE system architecture shownby an LTE/EUTRAN and its evolved packet core interworking with anexisting GERAN, UTRAN, and their GPRS Core. The LTE/EUTRAN comprises anE-Node B that is connected (S1) to an evolved packet core containing amobility management entity/user plane entity (MME/UPE) and an inter ASanchor Gateway. The Evolved Packet Core connects (S6) to a homesubscriber service (HSS), and connects (S7) to a Policy and ChargingRules (PCRF). The inter AS Anchor gateway connects (Gi) to Operator IPServers (such as IMS, PSS), connects (S2) to a Non-3GPP IP Accessnetwork 108, and connects (S2) to a WLAN 3GPP IP Access network 109.

The GPRS Core shown in FIG. 1 of these prior art references comprises aServing GPRS Support Node (SGSN) which is responsible for MobilityManagement, Access Procedures, and User Plane Control. The GPRS Corealso comprises a Gateway GPRS Support Node (GGSN), where the network isconnected to external networks and other operator servers. The Non-3GPPIP access network 108 includes connections to other technologies thatare developed in other standard Forums such as 3GPP2 (CDMA2000) andWiMAX (IEEE 802.16 system). The WLAN 3GPP IP access network has WLANsincorporated into 3GPP systems via interworking architecture defined in3GPP. These identified patent references, however, do not address theoptimized handover procedures and system for an idle mode handover ofuser equipment from a 3GPP (EUTRAN) to a non-3GPP (HRPD cdma2000) systemwhere the user equipment wishes to maintain connectivity with multiplePDN networks.

The Technical Specification 3GPP TS 23.402 V8.1.1 (2008 March) describesa 3rd Generation Partnership Project (3GPP) Technical Specification forenhancements and interactions with non-3GPP accesses. The particularversion of the Technical Specification is Release 8, which describes thegeneral network resources, entities, functions, and handover proceduresfor certain inter-technology combination handover systems, protocols,and procedures. Like the above-identified references, this TechnicalSpecification also fails to address the optimized handover proceduresand system for an idle mode handoff of user equipment from a 3GPP(EUTRAN) to a non-3GPP system (HRPD cdma 2000) where the user equipmentwishes to maintain connectivity with multiple PDN networks. It would bebeneficial to have a method and system that could support such an idlemode handover while maintaining the user equipment's connectivity tomultiple PDN networks.

SUMMARY OF THE INVENTION

The present invention provides a method and system for supporting anoptimized idle mode handoff of user equipment from a 3GPP (EUTRAN) to anon-3GPP system (HRPD, cdma2000) where the user equipment wishes tomaintain connectivity with multiple PDN networks. Namely, when the userequipment establishes its presence with the non-3GPP system in idlemode, the user equipment will provide an indication to the access nodeon the non-3GPP system so that the access node in that non-3GPP systemcontacts the appropriate entity (HSS or AAA) on the home network for theuser equipment to download the addresses of the multiple PDN gatewaythat are currently in use by the user equipment. This indication to thenon-3GPP access node, the contact message from the access node to thehome network, and the response from the home network to the access nodeon the non-3GPP system are novel features that are not shown in theprior art, and provide the access node with sufficient information tomaintain multiple PDN connectivity to the user equipment during an idlemode handover.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention will become more readilyunderstood from the following detailed description and appended claimswhen read in conjunction with the accompanying drawings in which likenumerals represent like elements and in which:

FIG. 1 is a mobile IP-based communication system showing the userequipment, the 3GPP based network, the non-3GPP network and the multiplePDN connections to the user equipment, and,

FIG. 2 is a handover protocol of the user equipment to the non-3GPPsystem with the disclosure of the indication message, the access noderequest message to the home network, and the response to the accessnode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the present invention proposes a solution to theidle mode handover of user equipment from a 3GPP network to a non-3GPPnetwork that includes providing the access node on the non-3GPP networkwith the addresses for the multiple PDN gateway connections currentlybeing used by the user equipment, which are shown as PDN Gateway 1 110and PDN Gateway 2 115. The handover occurs in FIG. 1 from the E-UTRANnetwork 102 to the HRPD network 120 in the present invention so thatmultiple PDN network connectivity can be maintained with the userequipment 101 during the idle mode handover. In this example, theE-UTRAN network 102 is a 3GPP network called the source network, and theHRPD network 120 is a non-3GPP network called the target network.

In the prior art, the HSS on the home network (not shown in FIG. 1)receives the values of the addresses of all allocated PDN Gateways (110and 115) and the corresponding PDN information for a given userequipment 101 assigned to the HSS's home network from both the 3GPP AAA(not shown) and also from the MME 135, depending on the currently in-useaccess. The HSS on the home network is responsible for the storage ofPDN Gateway address information. In an active mode handover in the priorart, if user equipment is attached to a non-3GPP access and it alreadyhas assigned PDN Gateways (110 and 115) due to a previous attach in a3GPP access, the HSS on the home network provides the IP address(es) ofthe already allocated PDN Gateway(s) (110 and 115) with thecorresponding PDN information to the 3GPP AAA server over the SWxreference point. The PDN gateway's address(es) is sent during the attachprocedure in the non-3GPP access. Also in active mode, if user equipment101 attaches to a 3GPP access and it already has an assigned PDNGateway(s) 110 and 115 due to a previous attach in a non-3GPP access,the HSS provides the IP address(es) of the already allocated PDNGateway(s) (110 and 115) with the corresponding PDN information to theMME over the S6 a reference point, and the PDN gateway address(es) issent during the attach procedure in the 3GPP access.

No prior art procedures support the handover of user equipment in anon-active, idle mode so that connectivity can be maintained withmultiple PDN connections, and no prior art procedures allow for thedirect interaction between the access node of the non-3GPP network andthe HSS entity/AAA server on the home entity to acquire the multiple PDNgateway addresses. By “idle mode,” the applicant means that the systemis not operating in an active or connected mobility mode procedure, andthe “idle mode” can be characterized by an idle mobility procedure or aradio link failure scenario. The present invention supports such an“idle mode” transfer of user equipment with multiple PDN gatewayconnections.

Referring to FIG. 1, the network 100 shows the various networkcomponents involved with the idle mode inter-technology handover withconnectivity to multiple PDN networks. The user equipment 101 is coupledto the E-UTRAN network (3GPP) 102 through connection 103. When referredto hereafter, the terminology user equipment (UE) includes, but is notlimited to, a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), acomputer, or any other type of user device capable of operating in awireless environment.

The E-UTRAN network 102 is coupled through S1-U connection 112 to theServing Gateway 105, which is coupled to PDN Gateway 1 110 and PDNGateway 2 115 through connections S5 116 and 117, respectively. The PDNGateway 1 110 and PDN Gateway 2 115 couple the multiple PDN networks 150and 151, which are coupled by connections 143 and 144, respectively.SGi1 142 and SGi2 141 interfaces are coupled to PDN sources of datalocated on the Internet 150 through connections 151 and 152,respectively. Maintaining these multiple PDN connections during an idlehandover of the user equipment 101 from the E-UTRAN 102 system to anon-3GPP system, such as the HRPD system 120 shown in FIG. 1 is theprimary focus of the present invention.

The E-UTRAN network 102 is coupled through S1-MME connection 137 to theMobility Management Entity (MME) 135, which has an internal S10connection 113. The MME 135 is coupled to the Serving Gateway 105through connection S11 111, and the MME 135 is couple to the HRPD AccessNode 130 on the HRPD system 120 through S101 connection 132. The HRPDAccess Node 130 is coupled to the Packet Data Switching Node (PDSN) 125through the Interoperability Specification (IOS) connection 127. ThePDSN 125 is sometimes called the HRPD Serving Gateway (HSGW), which iscoupled to the PDN Gateway 1 110 and PDN Gateway 2 115 through the S2 aconnections 122 and 121, respectively.

The HRPD Access Node 130 will be provided with a connection request inidle mode from the user equipment 101, and the connection request willinclude an indication from the user equipment 101 that multiple PDNconnections are in use by the user equipment 101. This indication willprompt the HRPD Access Node 130 to send a request to the home subscriberstorage (HSS) entity and/or Authentication, Authorization and Accounting(AAA) server located on the home network (not shown in FIG. 1) assignedto the user equipment 101 to request the addresses of all PDN gateways(110 and 115) currently in use by the user equipment. The HSS entityand/or AAA server on the home network will respond to the request withthe addresses of all PDN gateways currently in use by the user equipment101 so the multiple PDN connectivity with the user equipment 101 can bemaintained during the idle mode handover.

In FIG. 2, the handover communication protocol is shown starting at step310 when the user equipment is designated as being in idle mode. Theuser equipment makes a decision to “re-select” its cell location in step315 to the non-3GPP network, and the user equipment 101 sends a HRPDConnection Request message in step 320 to the HRPD Access Node 130. ThisHRPD Connection Request message in step 320 would include an indicationthat the user equipment 101 is currently using multiple PDN connections.

In response to this indication, the HRPD Access Node 130 will send arequest message 322 to the AAA server/HSS entity 175 located on the homenetwork assigned to the user equipment in step 322. In step 322, the AAAserver/HSS entity 175 will respond to that request with the addressesfor the multiple PDN gateways and any other relevant informationregarding the PDN connections currently in use by the user equipment101, such as IP addresses of the already allocated PDN Gateway(s) (110and 115) and corresponding PDN information.

The HRPD Access Node will transmit an A11 registration request messageto the PDSN 125 on the non-3GPP network in step 325, which will includethe address information for the multiple PDN gateways 110 and 115currently in use by the user equipment. The PDSN 125 will use theaddress information to send a PMIP message to the PDN gateways 110 and115 in step 330, which will be acknowledged by response messages to thePDSN 125 from the PDN gateways 110 and 115 in step 335. The PDN gateways110 and 115 will send messages to the PCRF entities in step 340, andreceive a response from the PCRF entities in step 345.

After receiving the response from the PDN gateways 110 and 115 in step335, the PDSN on the non-3GPP network will send an A11 registrationreply to the HRPD Access Node 130 in step 350. The HRPD Access Node willsend the user equipment 101 an HRPD Traffic Channel Assignment in step360 to establish the connection with the user equipment 101. The userequipment 101 will then send an HRPD TCC (traffic channel complete)message to the HRPD Access Node 130 in step 370. The user equipment 101may also send an HRPD Connection Release message to the HRPD Access Node130 in step 380. After these connections are established, any futureuser equipment 101 communication traffic may flow in both the uplink anddownlink directions via the non-3GPP network, including traffic throughthe multiple PDN connections which have been maintained after thehandover to the non-3GPP network.

While preferred embodiments of the invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit and teachings of the invention. Theembodiments described herein are exemplary only, and are not intended tobe limiting. Many variations and modifications of the inventiondisclosed herein are possible and are within the scope of the invention.

1. A method for maintaining connectivity between user equipment andmultiple PDN connections during an idle mode handover from a sourcenetwork to a target network, comprising the steps of: receiving aregistration request message at an access node on target network fromthe user equipment, said registration request message establishing thepresence of said user equipment with the target network and including anindication that multiple PDN connections are currently in use by theuser equipment; transmitting a request message from the access node onthe target network to a home subscriber storage entity on a home networkassigned to the user equipment; receiving a response message from thehome subscriber storage entity on the home network assigned to the userequipment at the access node on the target network, said responsemessage including the addresses for all PDN gateways that support themultiple PDN connections to the user equipment; transmitting themultiple PDN gateway addresses to a control entity on the target networkso that access can be established with the multiple PDN gateways tomaintain the PDN connections with the user equipment after the handoverof user equipment communications to the target network.
 2. The method inclaim 1 wherein the source network operates under the 3GPPcommunications protocol.
 3. The method in claim 1 wherein the targetnetwork operates under a non-3GPP communications protocol.
 4. The methodin claim 1 wherein the address information for the PDN gateways alsoincludes all IP addresses of the PDN gateways with corresponding PDNinformation.
 5. The method in claim 1 wherein the control entity on thetarget network is an entity called PDSN entity or HRPD Serving Gateway.6. The method in claim 5 wherein the PDSN control entity establishesaccess with the multiple PDN gateways using a PMIP binding updaterequest message.
 7. The method in claim 1 wherein the access node on thetarget network is an HRPD access node entity.
 8. The method in claim 1wherein the request message received by the access node is an HRPDconnection request message.
 9. The method in claim 1 wherein the homesubscriber storage entity can be a AAA server on the home network.
 10. Amethod for maintaining connectivity between user equipment and multiplePDN connections during an idle mode handover from a source network to atarget network, comprising the steps of: receiving a registrationrequest message at an HRPD access node on a target network from the userequipment, said registration request message establishing the presenceof said user equipment with the target network and including anindication that multiple PDN connections are currently in use by theuser equipment; transmitting a request message from the HRPD access nodeon the target network to a home subscriber storage entity on a homenetwork assigned to the user equipment; receiving a response messagefrom the home subscriber storage entity on the home network assigned tothe user equipment at the HRPD access node on the target network, saidresponse message including the addresses for all PDN gateways thatsupport the multiple PDN connections to the user equipment; transmittingthe multiple PDN gateway addresses to a PDSN control entity on thetarget network so that access can be established with the multiple PDNgateways to maintain the PDN connections with the user equipment afterthe handover of user equipment communications to the target network. 11.The method in claim 10 wherein the source network operates under the3GPP communications protocol.
 12. The method in claim 10 wherein thetarget network operates under a non-3GPP communications protocol. 13.The method in claim 10 wherein the address information for the PDNgateways also includes all IP addresses of the PDN gateways withcorresponding PDN information.
 14. The method in claim 10 wherein thePDSN control entity establishes access with the multiple PDN gatewaysusing a PMIP binding update request message.
 15. The method in claim 10wherein the access node on the target network is an HRPD connectionrequest message.
 16. The method in claim 10 wherein the home subscriberstorage entity can be a AAA server on the home network.
 17. A targetcommunications network used to maintain connectivity between userequipment and multiple PDN connections during an idle mode handover,comprising: an HRPD access node on the target communications networkcoupled to user equipment associated with a source network, said HRPDaccess node receives a registration request message from the userequipment that establishes the presence of the user equipment with thetarget network and includes an indication that multiple PDN connectionsare currently in use by the user equipment, said HRPD access nodetransmits a request message to a home subscriber storage entity on ahome network assigned to the user equipment and receives a responsemessage from the home subscriber storage entity on the home networkassigned to the user equipment at the HRPD access node on the targetnetwork, said response message includes the addresses for all PDNgateways that support the multiple PDN connections to the userequipment; a control entity on the target communications network coupledto the HRPD access node, said control entity receiving the multiple PDNgateway addresses from the HRPD access node and establishing accessconnections between the target communications network and the multiplePDN gateways so as to maintain the PDN connections with the userequipment after the handover of user equipment communications to thetarget network.
 18. The method in claim 17 wherein the source networkoperates under the 3GPP communications protocol.
 19. The method in claim17 wherein the target network operates under a non-3GPP communicationsprotocol.
 20. The method in claim 17 wherein the address information forthe PDN gateways also includes all IP addresses of the PDN gateways withcorresponding PDN information.
 21. The method in claim 17 wherein thecontrol entity establishes access with the multiple PDN gateways using aPMIP binding update request message.
 22. The method in claim 17 whereinthe access node on the target network is an HRPD connection requestmessage.
 23. The method in claim 17 wherein the home subscriber storageentity can be a AAA server on the home network.